Air conditioner and control method thereof

ABSTRACT

An air conditioner that improves efficiency of an inverter compressor by injecting an intermediate pressure refrigerant to the inverter compressor during heating or cooling and a control method thereof are provided.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the priority benefit of Korean Patent Application No. 2012-0088936, filed on Aug. 14, 2012 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference.

BACKGROUND

1. Field

Embodiments relate to an air conditioner and a control method thereof.

2. Description of the Related Art

In general, an air conditioner includes an outdoor unit and multiple indoor units. Here, a compressor, a four-way valve, an outdoor heat exchanger, and an expansion valve are provided in the outdoor unit, and an indoor heat exchanger is provided in each of the multiple indoor units.

The compressor, the four-way valve, the outdoor heat exchanger, the expansion valve, and the indoor heat exchanger are connected with each other by a refrigerant pipe that is applied for performing a cooling or a heating cycle.

The compressor includes an inverter compressor whose capacity is variable and a constant speed type compressor whose capacity is not variable, and one inverter compressor and multiple constant speed type compressors are used together due to the expensive price of the inverter compressor.

In the above-described system, since one inverter compressor is used, the whole system may heavily depend on a driving situation of the inverter compressor, and for example, may stop when the inverter compressor is broken.

In addition, in a state in which one inverter compressor first starts to control and all constant speed type compressors of a system are operated, superheated steam injection cannot be used until the inverter compressor can be operated in a region in which the superheated steam injection is possible. Accordingly, a region in which the superheated steam injection can be performed is limited, and there is no gain due to the superheated steam injection at the time of high-capacity operation. As a result, generally, the superheated injection is not used during cooling.

SUMMARY

In an aspect of one or more embodiments, there is provided an air conditioner that improves efficiency of an inverter compressor by injecting an intermediate pressure refrigerant to the inverter compressor during heating and cooling, and a control method thereof.

In an aspect of one or more embodiments, there is provided an air conditioner includes: a dual inverter compressor that includes a first inverter compressor and a second inverter compressor and compresses a refrigerant at a high temperature and at a high pressure; an indoor heat exchanger that liquefies the refrigerant supplied from the dual inverter compressor; an expansion valve that decompresses and expands the refrigerant supplied from the indoor heat exchanger; an outdoor heat exchanger that vaporizes the refrigerant supplied from the expansion valve; a bypass pipe that is bypassed in a refrigerant pipe for connecting the indoor heat exchanger and the outdoor heat exchanger, and in which an electric expansion valve is installed; an inner heat exchanger that is provided between the indoor heat exchanger and the outdoor heat exchanger and is connected with the bypass pipe to generate an intermediate pressure refrigerant through heat exchange of the refrigerant moved from the indoor heat exchanger to the outdoor heat exchanger and the refrigerant bypassed to the bypass pipe; an intermediate pressure refrigerant guide pipe that guides the intermediate pressure refrigerant generated through the heat exchange in the inner heat exchanger to the dual inverter compressor, and in which an intermediate pressure refrigerant shut-off valve for controlling injection of the intermediate pressure refrigerant to the dual inverter compressor or controlling the injection to be prevented, and an intermediate pressure refrigerant spraying port for spraying the intermediate pressure refrigerant that has passed through the intermediate pressure refrigerant shut-off valve to the dual inverter compressor are installed; and an intermediate pressure refrigerant branch pipe that is branched in the intermediate pressure refrigerant guide pipe, and in which an opening and closing valve for controlling the intermediate pressure refrigerant to be injected to the dual inverter compressor along the intermediate pressure refrigerant guide pipe is installed.

The inner heat exchanger may perform heat exchange between the refrigerant that is moved from the indoor heat exchanger to the outdoor heat exchanger and the refrigerant that is bypassed to the bypass pipe and enters the inner heat exchanger, so that the refrigerant moved from the indoor heat exchanger to the outdoor heat exchanger is supercooled and the refrigerant bypassed to the bypass pipe and entering the inner heat exchanger is superheated.

The air conditioner may further include an accumulator that is provided so as to be connected with the intermediate pressure refrigerant branch pipe, and stores the intermediate pressure refrigerant injected through the intermediate pressure refrigerant branch pipe when the opening and closing valve is opened.

Also, the intermediate pressure refrigerant branch pipe may be provided so as to be connected to a fourth refrigerant pipe and enable the intermediate pressure refrigerant injected through the intermediate pressure refrigerant branch pipe to be supplied to the dual inverter compressor together with a refrigerant moved from the outdoor heat exchanger to the dual inverter compressor when the opening and closing valve is opened.

In addition, the intermediate pressure refrigerant shut-off valve may include a first intermediate pressure refrigerant shut-off valve for controlling injection of the intermediate pressure refrigerant to the first inverter compressor and a second intermediate pressure refrigerant shut-off valve for controlling injection of the intermediate pressure refrigerant to the second inverter compressor.

In addition, a muffler may be provided between the first inverter compressor and the first intermediate pressure refrigerant shut-off valve and between the second inverter compressor and the second intermediate pressure refrigerant shut-off valve.

Moreover, the air conditioner may further include a control unit that controls the electric expansion valve, the opening and closing valve, and the intermediate pressure refrigerant shut-off valve.

In an aspect of one or more embodiments, there is provided an air conditioner includes: a dual inverter compressor that includes a first inverter compressor and a second inverter compressor and compresses a refrigerant at a high temperature and at a high pressure; an outdoor heat exchanger that liquefies the refrigerant supplied from the dual inverter compressor; an expansion valve that decompresses and expands the refrigerant supplied from the outdoor heat exchanger; an indoor heat exchanger that vaporizes the refrigerant supplied from the expansion valve; a bypass pipe that is bypassed in a refrigerant pipe for connecting the outdoor heat exchanger and the indoor heat exchanger, and in which an electric expansion valve is installed; an inner heat exchanger that is provided between the outdoor heat exchanger and the indoor heat exchanger and is connected with the bypass pipe to generate an intermediate pressure refrigerant through heat exchange of the refrigerant moved from the outdoor heat exchanger to the indoor heat exchanger and the refrigerant bypassed to the bypass pipe; an intermediate pressure refrigerant guide pipe that guides the intermediate pressure refrigerant generated through the heat exchange in the inner heat exchanger to the dual inverter compressor, and in which an intermediate pressure refrigerant shut-off valve for controlling injection of the intermediate pressure refrigerant to the dual inverter compressor or controlling the injection to be prevented and an intermediate pressure refrigerant spraying port for spraying the intermediate pressure refrigerant that passed through the intermediate pressure refrigerant shut-off valve to the dual inverter compressor are installed; and an intermediate pressure refrigerant branch pipe that connects the intermediate pressure refrigerant guide pipe and an accumulator, and in which an opening and closing valve for controlling the intermediate pressure refrigerant to be injected to the dual inverter compressor along the intermediate pressure refrigerant guide pipe or to be discharged to the accumulator is installed.

The inner heat exchanger may perform heat exchange between the refrigerant that is moved from the outdoor heat exchanger to the indoor heat exchanger and the refrigerant that is bypassed to the bypass pipe and enters the inner heat exchanger, so that the refrigerant moved from the outdoor heat exchanger to the indoor heat exchanger is supercooled and the refrigerant bypassed to the bypass pipe and entering the inner heat exchanger is superheated.

The air conditioner may further include an accumulator that is provided so as to be connected with the intermediate pressure refrigerant branch pipe, and stores the intermediate pressure refrigerant injected through the intermediate pressure refrigerant branch pipe when the opening and closing valve is opened.

Also, the intermediate pressure refrigerant branch pipe may be provided so as to be connected to a fourth refrigerant pipe, and enable the intermediate pressure refrigerant injected through the intermediate pressure refrigerant branch pipe to be supplied to the dual inverter compressor together with a refrigerant moved from the indoor heat exchanger to the dual inverter compressor when the opening and closing valve is opened.

In addition, the intermediate pressure refrigerant shut-off valve may include a first intermediate pressure refrigerant shut-off valve for controlling injection of the intermediate pressure refrigerant to the first inverter compressor and a second intermediate pressure refrigerant shut-off valve for controlling injection of the intermediate pressure refrigerant to the second inverter compressor.

In addition, a muffler may be provided between the first inverter compressor and the first intermediate pressure refrigerant shut-off valve and between the second inverter compressor and the second intermediate pressure refrigerant shut-off valve.

Moreover, the air conditioner may further include a control unit that controls the electric expansion valve, the opening and closing valve, and the intermediate pressure refrigerant shut-off valve.

In an aspect of one or more embodiments, there is provided a method for controlling a heating operation of an air conditioner including a dual inverter compressor having a first inverter compressor and a second inverter compressor, an indoor heat exchanger, and an outdoor heat exchanger, the method includes: enabling a partial refrigerant to be expanded in a bypass pipe that is bypassed from a refrigerant pipe for connecting the indoor heat exchanger and the outdoor heat exchanger by opening an electric expansion valve installed in the bypass pipe; generating an intermediate pressure refrigerant by supplying the refrigerant of the bypass pipe to the inner heat exchanger installed in the refrigerant pipe for connecting the indoor heat exchanger and the outdoor heat exchanger; shutting off an opening and closing valve that is provided in an intermediate pressure refrigerant branch pipe branched in an intermediate pressure refrigerant guide pipe for connecting the inner heat exchanger and the dual inverter compressor so that the intermediate pressure refrigerant is moved through the intermediate pressure refrigerant guide pipe; and enabling the intermediate pressure refrigerant to be injected to the dual inverter compressor through the intermediate pressure refrigerant guide pipe by opening the intermediate pressure refrigerant shut-off valve provided in the intermediate pressure refrigerant guide pipe.

Here, when the electric expansion valve is opened, the refrigerant bypassed to the bypass pipe may be expanded in the electric expansion valve and then injected to the inner heat exchanger to be heat-exchanged with the refrigerant moved from the indoor heat exchanger to the outdoor heat exchanger, the refrigerant moved from the indoor heat exchanger to the outdoor heat exchanger may be supercooled through heat exchange to be supplied to the outdoor heat exchanger, and the refrigerant bypassed to the bypass pipe may be supplied to the dual inverter compressor in a state of absorbing heat.

In an aspect of one or more embodiments, there is provided a method for controlling a heating operation of an air conditioner including a dual inverter compressor having a first inverter compressor and a second inverter compressor, an indoor heat exchanger, and an outdoor heat exchanger, the method includes: preventing a refrigerant from flowing to a bypass pipe, which is bypassed in a refrigerant pipe for connecting the indoor heat exchanger and the outdoor heat exchanger and is connected with an inner heat exchanger provided in the refrigerant pipe, by shutting off an electric expansion valve installed in the bypass pipe, so that an intermediate pressure refrigerant is prevented from being injected to the dual inverter compressor.

When the intermediate pressure refrigerant is prevented from being injected to the dual inverter compressor by shutting off the electric expansion valve, an opening and closing valve that is installed in an intermediate pressure refrigerant branch pipe branched in an intermediate pressure refrigerant guide pipe for connecting the inner heat exchanger and the dual inverter compressor may be maintained to be opened, so that an increase in piping stress due to an internal flow of the intermediate pressure refrigerant guide pipe is prevented.

In addition, when the intermediate pressure refrigerant is prevented from being injected to the dual inverter compressor by shutting off the electric expansion valve and opening the opening and closing valve, the intermediate pressure refrigerant shut-off valve provided in the intermediate pressure refrigerant guide pipe may be maintained to be opened, so that chattering that occurs when the refrigerant flows in a direction opposite to a refrigerant flow direction of the intermediate pressure refrigerant shut-off valve, and occurrence of vibration of the intermediate pressure refrigerant guide pipe are reduced.

In an aspect of one or more embodiments, there is provided a method for controlling a heating operation of an air conditioner including a dual inverter compressor having a first inverter compressor and a second inverter compressor, an indoor heat exchanger, and an outdoor heat exchanger, the method that prevents injection of an intermediate pressure refrigerant to the dual inverter compressor and controls a refrigerant moved from the indoor heat exchanger to the outdoor heat exchanger to be supercooled, the method includes: enabling a refrigerant to be bypassed to a bypass pipe by opening an electric expansion valve installed in the bypass pipe that is bypassed in a refrigerant pipe for connecting the indoor heat exchanger and the outdoor heat exchanger and connected to an inner heat exchanger provided in the refrigerant pipe; and preventing the intermediate pressure refrigerant from being injected to the dual inverter compressor by opening an opening and closing valve installed in an intermediate pressure refrigerant branch pipe branched in an intermediate pressure refrigerant guide pipe for connecting the inner heat exchanger and the dual inverter compressor so that the intermediate pressure refrigerant generated in the inner heat exchanger is moved through the intermediate pressure refrigerant branch pipe to be stored in an accumulator connected with the intermediate pressure refrigerant branch pipe.

When the intermediate pressure refrigerant is prevented from being injected to the dual inverter compressor by opening the electric expansion valve and the opening and closing valve, an intermediate pressure refrigerant shut-off valve provided in the intermediate pressure refrigerant guide pipe may be maintained to be opened, so that chattering that occurs when the refrigerant flows in a direction opposite to a refrigerant flow direction of the intermediate pressure refrigerant shut-off valve, and occurrence of vibration of the intermediate pressure refrigerant guide pipe are reduced.

In an aspect of one or more embodiments, there is provided a method for controlling a cooling operation of an air conditioner including a dual inverter compressor having a first inverter compressor and a second inverter compressor, an indoor heat exchanger, and an outdoor heat exchanger, the method includes: enabling a partial refrigerant to be expanded in a bypass pipe that is bypassed from a refrigerant pipe for connecting the indoor heat exchanger and the outdoor heat exchanger by opening an electric expansion valve installed in the bypass pipe; generating an intermediate pressure refrigerant by supplying the refrigerant of the bypass pipe to the inner heat exchanger installed in the refrigerant pipe for connecting the indoor heat exchanger and the outdoor heat exchanger; shutting off an opening and closing valve that is provided in an intermediate pressure refrigerant branch pipe branched in an intermediate pressure refrigerant guide pipe for connecting the inner heat exchanger and the dual inverter compressor so that the intermediate pressure refrigerant is moved through the intermediate pressure refrigerant guide pipe; and enabling the intermediate pressure refrigerant to be injected to the dual inverter compressor through the intermediate pressure refrigerant guide pipe by opening the intermediate pressure refrigerant shut-off valve provided in the intermediate pressure refrigerant guide pipe.

When the electric expansion valve is opened, the refrigerant bypassed to the bypass pipe may be expanded in the electric expansion valve and then injected to the inner heat exchanger to be heat-exchanged with the refrigerant moved from the outdoor heat exchanger to the indoor heat exchanger, the refrigerant moved from the outdoor heat exchanger to the indoor heat exchanger may be supercooled through heat exchange to be supplied to the indoor heat exchanger, and the refrigerant bypassed to the bypass pipe may be supplied to the dual inverter compressor in a state of absorbing heat.

In an aspect of one or more embodiments, there is provided a method for controlling a cooling operating of an air conditioner including a dual inverter compressor having a first inverter compressor and a second inverter compressor, an indoor heat exchanger, and an outdoor indoor exchanger, the method includes: preventing a refrigerant from flowing to a bypass pipe that is bypassed in a refrigerant pipe for connecting the outdoor heat exchanger and the indoor heat exchanger and is connected with an inner heat exchanger provided in the refrigerant pipe, by shutting off an electric expansion valve installed in the bypass pipe, so that an intermediate pressure refrigerant is prevented from being injected to the dual inverter compressor.

When the intermediate pressure refrigerant is prevented from being injected to the dual inverter compressor by shutting off the electric expansion valve, an opening and closing valve that is installed in an intermediate pressure refrigerant branch pipe branched in an intermediate pressure refrigerant guide pipe for connecting the inner heat exchanger and the dual inverter compressor may be maintained to be opened, so that an increase in piping stress due to an internal flow of the intermediate pressure refrigerant guide pipe is prevented.

In addition, when the intermediate pressure refrigerant is prevented from being injected to the dual inverter compressor by shutting off the electric expansion valve and opening the opening and closing valve, the intermediate pressure refrigerant shut-off valve provided in the intermediate pressure refrigerant guide pipe may be maintained to be opened, so that chattering that occurs when the refrigerant flows in a direction opposite to a refrigerant flow direction of the intermediate pressure refrigerant shut-off valve, and occurrence of vibration of the intermediate pressure refrigerant guide pipe are reduced.

In an aspect of one or more embodiments, there is provided a method for controlling a cooling operation of an air conditioner including a dual inverter compressor having a first inverter compressor and a second inverter compressor, an indoor heat exchanger, and an outdoor heat exchanger, the method that prevents injection of an intermediate pressure refrigerant to the dual inverter compressor and controls a refrigerant moved from the indoor heat exchanger to the outdoor heat exchanger to be supercooled, the method includes: enabling a refrigerant to be bypassed to a bypass pipe by opening an electric expansion valve installed in the bypass pipe that is bypassed in a refrigerant pipe for connecting the outdoor heat exchanger and the indoor heat exchanger and connected to an inner heat exchanger provided in the refrigerant pipe; and preventing the intermediate pressure refrigerant from being injected to the dual inverter compressor by opening an opening and closing valve installed in an intermediate pressure refrigerant branch pipe branched in an intermediate pressure refrigerant guide pipe for connecting the inner heat exchanger and the dual inverter compressor so that the intermediate pressure refrigerant generated in the inner heat exchanger is moved through the intermediate pressure refrigerant branch pipe to be stored in an accumulator connected with the intermediate pressure refrigerant branch pipe.

When the intermediate pressure refrigerant is prevented from being injected to the dual inverter compressor by opening the electric expansion valve and the opening and closing valve, an intermediate pressure refrigerant shut-off valve provided in the intermediate pressure refrigerant guide pipe may be maintained to be opened, so that chattering that occurs when that the refrigerant flows in a direction opposite to a refrigerant flow direction of the intermediate pressure refrigerant shut-off valve, and occurrence of vibration of the intermediate pressure refrigerant guide pipe are reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

These and/or other aspects of embodiments will become apparent and more readily appreciated from the following description of embodiments, taken in conjunction with the accompanying drawings of which:

FIGS. 1 and 2 are diagrams showing a configuration of an air conditioner according to an embodiment;

FIG. 3 is a diagram showing a configuration of a multi-air conditioner according to an embodiment;

FIG. 4 is a block diagram showing a state in which an air conditioner according to an embodiment is controlled by a control unit;

FIG. 5 is a diagram showing a process in which an intermediate pressure refrigerant is injected to a dual inverter compressor during a heating operation of an air conditioner according to an embodiment;

FIG. 6 is a block diagram showing control of the air conditioner of FIG. 4;

FIG. 7 is a diagram showing a case in which injection of an intermediate pressure refrigerant to a dual inverter compressor is prevented during a heating operation of an air conditioner according to an embodiment and supercooling control is not required;

FIG. 8 is a block diagram showing control of the air conditioner of FIG. 6;

FIG. 9 is a diagram showing a case in which injection of an intermediate pressure refrigerant to a dual inverter compressor is prevented during a heating operation of an air conditioner according to an embodiment and supercooling control is required;

FIG. 10 is a block diagram showing control of the air conditioner of FIG, 9;

FIG. 11 is a diagram showing a process in which an intermediate pressure refrigerant is injected to a dual inverter compressor during a cooling operation of an air conditioner according to an embodiment;

FIG. 12 is a block diagram showing control of the air conditioner of FIG. 11;

FIG. 13 is a diagram showing a case in which injection of an intermediate pressure refrigerant to a dual inverter compressor is prevented during a cooling operation of an air conditioner according to an embodiment and supercooling control is not required;

FIG. 14 is a block diagram showing control of the air conditioner of FIG. 13;

FIG. 15 is a diagram showing a case in which injection of an intermediate pressure refrigerant to a dual inverter compressor is prevented during a cooling operation of an air conditioner according to an embodiment and supercooling control is required; and

FIG. 16 is a block diagram showing control of the air conditioner of FIG. 15.

DETAILED DESCRIPTION

Reference will now be made in detail to embodiments, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout.

As shown in FIGS. 1 and 2, an air conditioner includes an outdoor unit 1 and an indoor unit 2. In the outdoor unit 1, dual inverter compressors 10 that are sequentially connected to a refrigerant pipe so as to configure a closed circuit, a four-way valve 3 for switching between heating and cooling, an outdoor heat exchanger 4, an expansion valve 6 are provided, and in the indoor unit 2, an indoor heat exchanger 5 is provided.

At the time of a heating operation, a refrigerant is circulated in such a manner that the refrigerant is compressed in the dual inverter compressor 10 at a high temperature and at a high pressure, the compressed refrigerant is supplied to the indoor heat exchanger 5 to be liquefied in the indoor heat exchanger 5, the liquefied refrigerant is supplied to the expansion valve 6 to be decompressed and expanded, the decompressed and expanded refrigerant is supplied to the outdoor heat exchanger 4 to be vaporized in the outdoor heat exchanger 4, and then the vaporized refrigerant is supplied again to the dual inverter compressor 10.

At the time of cooling operation, a refrigerant is circulated in such a manner that the refrigerant is compressed in the dual inverter compressor 10 at a high temperature and at a high pressure, the compressed refrigerant is supplied to the outdoor heat exchanger 14 to be liquefied in the outdoor heat exchanger, the liquefied refrigerant is supplied to the expansion valve 6 to be decompressed and expanded, the decompressed and expanded refrigerant is supplied to the indoor heat exchanger 5 to be vaporized in the indoor heat exchanger 5, and then the vaporized refrigerant is supplied again to the dual inverter compressor 10.

As shown in FIG. 3, an air conditioner may be configured as a multi-air conditioner including a plurality of indoor heat exchangers 5.

When the air conditioner is configured as the multi-air conditioner, electric expansion valves 31, 32, and 33 may be provided for each of the plurality of indoor heat exchangers 5. When efficiency of the dual inverter compressor 10 is reduced during heating and cooling operations, the air conditioner may improve the efficiency of the dual inverter compressor 10 by injecting an intermediate pressure refrigerant to the dual inverter compressor 10.

As shown in FIGS. 1 and 2, in order for the intermediate pressure refrigerant to be injected to the dual inverter compressor 10, the air conditioner may include an inner heat exchanger 20 that is provided between the indoor heat exchanger 5 and the outdoor heat exchanger 4 to generate the intermediate pressure refrigerant through heat exchange, a bypass pipe B1 that is bypassed in refrigerant pipes P2 and P3 for connecting the indoor heat exchanger 5 and the outdoor heat exchanger 4 and connected to the inner heat exchanger 20, an electric expansion valve 30 that is provided in the bypass pipe B1 and controls a refrigerant to enter the bypass pipe B1 or the entering of the refrigerant to be prevented, an intermediate pressure refrigerant spraying port 40 that is provided in an intermediate pressure refrigerant guide pipe P5 for guiding the intermediate pressure refrigerant generated in the inner heat exchanger 20 to the dual inverter compressor 10 and spraying the intermediate pressure refrigerant to the dual inverter compressor 10, an opening and closing valve 50 that is provided in an intermediate pressure refrigerant branch pipe B2 branched in the intermediate pressure refrigerant guide pipe P5 and controls the intermediate pressure refrigerant to be injected to the dual inverter compressor 10 or the injection to be prevented, and an intermediate pressure refrigerant shut-off valve 60 that is provided in the intermediate pressure refrigerant guide pipe P5 and controls the intermediate pressure refrigerant to be injected to the dual inverter compressor 10 or the injection to be prevented.

The dual inverter compressor 10 includes a first inverter compressor 11 and a second inverter compressor 13, and two inverter compressors are provided in the drawing, but at least two inverter compressors may be provided.

The inner heat exchanger 20 may be provided between the indoor heat exchanger 5 and the outdoor heat exchanger 4, and have a plate-shaped structure or a double tube structure.

When the air conditioner performs a heating operation, a condensed refrigerant from the indoor heat exchanger 5 used as a condenser is moved to the outdoor heat exchanger 4 via the inner heat exchanger 20.

A part of the refrigerant moved from the indoor heat exchanger 5 to the outdoor heat exchanger 4 passes through the inner heat exchanger 20, is supplied to the outdoor heat exchanger 4 used as a vaporizer via the expansion valve 6, and then is vaporized.

The remaining part of the refrigerant moved from the indoor heat exchanger 5 to the outdoor heat exchanger 4 is bypassed through the bypass pipe B1, and enters the inner heat exchanger 20. In a process in which the refrigerant bypassed to the bypass pipe B1 passes through the bypass pipe B1, the refrigerant bypassed to the bypass pipe B1 passes through the electric expansion valve 30 provided in the bypass pipe B1, and enters the inner heat exchanger 20 in a state of being expanded.

The refrigerant that is bypassed to the bypass pipe B1 and enters the inner heat exchanger 20 is heat-exchanged with a refrigerant that passes through the inner heat exchanger 20 in the indoor heat exchanger 5 and is moved to the outdoor heat exchanger 4, the refrigerant that is moved from the indoor heat exchanger 5 to the outdoor heat exchanger 4 through heat exchange is supplied to the outdoor heat exchanger 4 in a state of being supercooled, and a refrigerant that is bypassed to the bypass pipe B1 and enters the inner heat exchanger 20 is superheated and injected to the dual inverter compressor 10 through the intermediate pressure refrigerant guide pipe P5 as an intermediate pressure refrigerant of a superheated steam state.

When the air conditioner performs a cooling operation, a condensed refrigerant from the outdoor heat exchanger 4 used as a condenser is moved to the indoor heat exchanger 5 via the inner heat exchanger 20, as shown in FIG. 2.

A part of the refrigerant moved from the outdoor heat exchanger 4 to the indoor heat exchanger 5 passes through the inner heat exchanger 20 via the expansion valve 6, is supplied to the indoor heat exchanger 5 used as a vaporizer, and then is vaporized.

Although not shown, at the time of the cooling operation, the expansion valve 6 is provided between the inner heat exchanger 20 and the indoor heat exchanger 5, so that a part of the refrigerant moved from the outdoor heat exchanger 4 to the indoor heat exchanger 5 passes through the inner heat exchanger 20, is supplied to the indoor heat exchanger 5 used as a vaporizer through the expansion valve 6, and then is vaporized.

The remaining part of the refrigerant moved from the outdoor heat exchanger 4 to the indoor heat exchanger 5 is bypassed through the bypass pipe B1 and enters the inner heat exchanger 20.

In a process in which the refrigerant bypassed to the bypass pipe B1 passes through the bypass pipe B1, the refrigerant bypassed to the bypass pipe B1 passes through the electric expansion valve 30 provided in the bypass pipe B1 and enters the inner heat exchanger 20 in a state of being expanded.

The refrigerant that is bypassed to the bypass pipe B1 and enters the inner heat exchanger 20 passes through the inner heat exchanger 20 in the outdoor heat exchanger 4 and is heat-exchanged with a refrigerant moved to the indoor heat exchanger 5, the refrigerant that is moved from the outdoor heat exchanger 4 to the indoor heat exchanger 5 through heat exchange is supplied to the indoor heat exchanger 5 in a state of being supercooled, and the refrigerant that is bypassed to the bypass pipe B1 and enters the inner heat exchanger 20 is injected to the dual inverter compressor 10 through the intermediate pressure refrigerant guide pipe P5 as an intermediate pressure refrigerant in a superheated steam state.

The bypass pipe B1 is provided so as to be bypassed in a second refrigerant pipe P2 and connected with the inner heat exchanger 20, so that the refrigerant bypassed to the bypass pipe B1 can enter the inner heat exchanger 20, and as shown in FIG. 2, the bypass pipe B1 is provided so as to be bypassed in a third refrigerant pipe P3 and connected with the inner heat exchanger 20, so that the refrigerant bypassed to the bypass pipe B1 can enter the inner heat exchanger 20.

The electric expansion valve 30 is provided in the bypass pipe B1, so that the refrigerant bypassed to the bypass pipe B1 can enter the inner heat exchanger 20 in a state of being expanded.

In addition, the refrigerant bypassed to the bypass pipe B1 is controlled to enter the inner heat exchanger 20 or the entering to be prevented depending on whether the electric expansion valve 30 is opened or closed.

When the electric expansion valve 30 is opened, the refrigerant bypassed to the bypass pipe B1 enters the inner heat exchanger 20 and is supercooled and superheated through heat exchange with the refrigerant moved from the indoor heat exchanger 5 to the outdoor heat exchanger 4 during heating within the inner heat exchanger 20, and is supercooled and superheated through heat exchange with the refrigerant moved from the outdoor heat exchanger 4 to the indoor heat exchanger 5 during cooling, so that the superheated refrigerant is moved through the intermediate pressure refrigerant guide pipe P5 as an intermediate pressure refrigerant of a superheated steam state to thereby be injected to the dual inverter compressor 10.

When the electric expansion valve 30 is closed, the refrigerant does not enter the bypass pipe B1, and therefore heat exchange within the inner heat exchanger 20 is not performed, and the intermediate pressure refrigerant is not generated in the inner heat exchanger 20, thereby preventing the intermediate pressure refrigerant from being injected to the dual inverter compressor 10.

The intermediate pressure refrigerant spraying port 40 is provided in the intermediate pressure refrigerant guide pipe P5 for guiding the intermediate pressure refrigerant generated through heat exchange in the inner heat exchanger 20 to be injected to the dual inverter compressor 10, and includes a first intermediate pressure refrigerant spraying port 41 for spraying the intermediate pressure refrigerant to the first inverter compressor 11 and a second intermediate pressure refrigerant spraying port 43 for spraying the intermediate pressure refrigerant to the second inverter compressor 13.

When efficiency of the dual inverter compressor 10 is reduced, the intermediate pressure refrigerant spraying port 40 may spray the intermediate pressure refrigerant generated in the inner heat exchanger 20 to the dual inverter compressor 10, whereby the efficiency of the dual inverter compressor 10 is improved.

When the efficiency of the dual inverter compressor 10 is reduced, an operating frequency of the dual inverter compressor 10 is increased or a discharge temperature is increased. Therefore, in order to improve the efficiency of the dual inverter compressor 10, the dual inverter compressor 10 should maintain the operating frequency at an optimal frequency or reduce the discharge temperature. By injecting the intermediate pressure refrigerant generated in the inner heat exchanger 20 to the dual inverter compressor 10, the dual inverter compressor 10 may maintain the operating frequency as the optimal frequency, or reduce the discharge temperature.

The opening and closing valve 50 is provided in the intermediate pressure refrigerant branch pipe B2 branched in the intermediate pressure refrigerant guide pipe P5, and the controls the intermediate pressure refrigerant generated in the inner heat exchanger 20 to be injected to the dual inverter compressor 10 or the injection to be prevented.

When the opening and closing valve 50 is closed, a path through which the intermediate pressure refrigerant is moved to an accumulator A through the intermediate pressure refrigerant branch pipe B2 is shut off, whereby the intermediate pressure refrigerant generated in the inner heat exchanger 20 is injected to the dual inverter compressor 10 through the intermediate pressure refrigerant guide pipe P5, and when the opening and closing valve 50 is opened, the intermediate pressure refrigerant generated in the inner heat exchanger 20 is moved along the intermediate pressure refrigerant branch pipe B2 branched in the intermediate pressure refrigerant guide pipe P5, and stored in the accumulator provided so as to be connected to the intermediate pressure refrigerant branch pipe B2.

Although not shown, the intermediate pressure refrigerant branch pipe B2 branched in the intermediate pressure refrigerant guide pipe P5 is provided so as to be connected directly to a fourth refrigerant pipe P4 without using the accumulator, and therefore, when the opening and closing valve 50 is opened, the intermediate pressure refrigerant injected through the intermediate pressure refrigerant branch pipe B2 can be supplied to the dual inverter compressor 10 together with the refrigerant moved from the outdoor heat exchanger 4 to the dual inverter compressor 10.

The above-described case is a case of heating operating, and in a case of cooling operating, when the opening and closing valve 50 is opened, the intermediate pressure refrigerant injected through the intermediate pressure refrigerant branch pipe B2 can be supplied to the dual inverter compressor 10 together with the refrigerant moved from the indoor heat exchanger 5 to the dual inverter compressor 10.

The intermediate pressure refrigerant shut-off valve 60 is provided in the intermediate pressure refrigerant guide pipe P5, and controls the intermediate pressure refrigerant to be injected to the dual inverter compressor 10 or the injection to be prevented.

The intermediate pressure refrigerant shut-off valve 60 includes a first intermediate pressure refrigerant shut-off valve 61 for controlling the intermediate pressure refrigerant to be injected to the first inverter compressor 11 or the injection to be prevented, and a second intermediate pressure refrigerant shut-off valve 63 for controlling the intermediate pressure refrigerant to be injected to the second inverter compressor 13 or the injection to be prevented.

When the intermediate pressure refrigerant shut-off valve 60 is opened, the intermediate pressure refrigerant moved along the intermediate pressure refrigerant guide pipe P5 is injected to the dual inverter compressor 10, and when the intermediate pressure refrigerant shut-off valve 60 is shut off, the intermediate pressure refrigerant is prevented from being injected to the dual inverter compressor 10.

Since the intermediate pressure refrigerant shut-off valve 60 has large variability of a pressure state front and rear, a chattering phenomenon easily occurs when a piston-like movement inside the intermediate pressure refrigerant shut-off valve 60 is inordinately and repeatedly turned on and off, and there are problems such as occurrence of noise and damage of the valve when the chattering phenomenon occurs.

The intermediate pressure refrigerant shut-off valve 60 may be provided as a two-way valve or one-way valve. In a case of the one-way valve, there is a disadvantage that the one-way valve is opened when a prescribed pressure or higher acts in a direction opposite to an intermediate pressure refrigerant flow direction, and in the two-way valve, on and off operation states of the valve may be maintained regardless of two-way pressure due to a check valve structure.

Accordingly, the two-way valve is mainly used as the intermediate pressure refrigerant shut-off valve 60, but is more expansive than the one-way valve.

In order to obtain effects of the two-way valve while using the inexpensive one-way valve as the intermediate pressure refrigerant shut-off valve 60, a muffler 70 is provided between the intermediate pressure refrigerant shut-off valve 60 and the intermediate pressure refrigerant spraying port 40.

The muffler 70 is provided between the intermediate pressure refrigerant shut-off valve 60 and the intermediate pressure refrigerant spraying port 40, and therefore a pressure pulsation transmitted from the dual inverter compressor 10 is reduced even when the one-way valve is used as the intermediate pressure refrigerant shut-off valve 60, thereby solving a chattering occurrence problem and a piping vibration problem due to the refrigerant flow within the refrigerant pipe.

As shown in FIG. 4, the electric expansion valve 30, the opening and closing valve 50, and the intermediate pressure refrigerant shut-off valve 60 may be opened or closed by the control unit 80.

Next, a control method of an air conditioner during heating or cooling operation will be described with reference to FIGS. 5 to 16.

In FIGS. 5, 9, 11, and 15, a movement path in which an intermediate pressure refrigerant generated in the inner heat exchanger 20 is injected to the dual inverter compressor 10 or the injection is prevented by control of the electric expansion valve 30, the opening and closing valve 50, and the intermediate pressure refrigerant shut-off valve 60 is shown as a bold arrow.

As shown in FIGS. 5 and 6, during a heating operation of an air conditioner, a high-temperature and high-pressure refrigerant discharged from the dual inverter compressor 10 passes through the four-way valve 3 along an arrow shown in the refrigerant pipe, and flows into the indoor heat exchanger 5 acting as a condenser through the first refrigerant pipe P1. The flowing-in high-temperature and high-pressure refrigerant is heat-exchanged with an indoor air of the outside of the indoor heat exchanger 5 in the indoor heat exchanger 5 to heat the indoor air.

A heating cycle is performed in such a manner that the refrigerant passing through the indoor heat exchanger 5 is moved through the second refrigerant pipe P2 and the third refrigerant pipe P3, expanded and decompressed via the expansion valve 6 provided in the third refrigerant pipe P3, flows into the outdoor heat exchanger 4, and then re-circulated to the dual inverter compressor 10 again through the fourth refrigerant pipe P4. In this instance, when efficiency of the dual inverter compressor is reduced, an operating frequency of the dual inverter compressor 10 is increased or a discharge temperature is increased. In order to improve the efficiency of the dual inverter compressor 10, the operating frequency of the dual inverter compressor 10 should be maintained at an optimal frequency or the discharge temperature should be reduced. Therefore, an intermediate pressure refrigerant is injected to the dual inverter compressor 10 in order to maintain the operating frequency of the dual inverter compressor 10 at the optimal frequency or reduce the discharge temperature.

In order to maintain the operating frequency of the dual inverter compressor 10 at the optimal frequency or reduce the discharge temperature, by performing heat-exchange between a refrigerant that is moved from the indoor heat exchanger 5 to the outdoor heat exchanger 4 in the inner heat exchanger 20 provided between the second refrigerant pipe P2 and the third refrigerant pipe P3 and a refrigerant that is bypassed to the bypass pipe B1 while being moved from the indoor heat exchanger 5 to the outdoor heat exchanger 4 and then enters the inner heat exchanger 20, an intermediate pressure refrigerant is generated and the generated intermediate pressure refrigerant is injected to the dual inverter compressor 10.

For this, first, in order for heat-exchange for generating the intermediate pressure refrigerant to be performed in the inner heat exchanger 20, a part of the refrigerant moved from the indoor heat exchanger 5 to the outdoor heat exchanger 4 is bypassed to the bypass pipe B1 by opening the electric expansion valve 30 provided in the bypass pipe B1.

The refrigerant bypassed to the inner heat exchanger 20 is heat-exchanged with the refrigerant moved from the indoor heat exchanger 5 to the outdoor heat exchanger 4 through the second refrigerant pipe P2 and the third refrigerant pipe P3 inside the inner heat exchanger 20, so that the refrigerant moved from the indoor heat exchanger 5 to the outdoor heat exchanger 4 through the heat-exchange is supercooled to be supplied to the outdoor heat exchanger 4, and the refrigerant bypassed to the inner heat exchanger 20 is superheated to flow along the intermediate pressure refrigerant guide pipe P5.

In order for the intermediate pressure refrigerant flowing along the intermediate pressure refrigerant guide pipe P5 to be guided to the dual inverter compressor 10, the opening and closing valve 50 provided in the intermediate pressure refrigerant branch pipe B2 branched in the intermediate pressure refrigerant guide pipe P5 is shut off.

When shutting off the opening and closing valve 50, the intermediate pressure refrigerant cannot be moved to the intermediate pressure refrigerant branch pipe B2, and therefore the intermediate pressure refrigerant flows along the intermediate pressure refrigerant guide pipe P5.

When the intermediate pressure refrigerant is moved along the intermediate pressure refrigerant guide pipe P5, the intermediate pressure refrigerant is injected to the dual inverter compressor 10 by opening the intermediate pressure refrigerant shut-off valve 60. When an operating frequency of the dual inverter compressor 10 is maintained at an optimal frequency, or a discharge temperature of the dual inverter compressor 10 is reduced, the dual inverter compressor 10 should be protected by preventing the intermediate pressure refrigerant from being injected to the dual inverter compressor 10.

In a case in which supercooling control is not required while the intermediate pressure refrigerant is prevented from being injected to the dual inverter compressor 10 by maintaining the operating frequency of the dual inverter compressor 10 at the optimal frequency or reducing the discharge temperature, in order for the intermediate pressure refrigerant to be prevented from being injected to the dual inverter compressor 10, the electric expansion valve 30 is shut off so that heat-exchange of the refrigerant is not performed in the inner heat exchanger 20, as shown in FIGS. 7 and 8.

When the electric expansion valve 30 is shut off, the refrigerant is prevented from flowing to the bypass pipe B1 and the intermediate pressure refrigerant is not generated in the inner heat exchanger 20, and therefore the intermediate pressure refrigerant is prevented from being injected to the dual inverter compressor 10.

In this instance, since the intermediate pressure refrigerant is prevented from being injected to the dual inverter compressor 10, the opening and closing valve 50 should be shut off, but in order to prevent an increase in piping stress due to an internal flow of the intermediate pressure refrigerant guide pipe P5, it is desirable that the opening and closing valve 50 be maintained to be opened.

In addition, since the intermediate pressure refrigerant is prevented from being injected to the dual inverter compressor 10, the intermediate pressure refrigerant shut-off valve 60 should be also shut off, but in order to reduce a chattering phenomenon that occurs when a refrigerant flows in a direction opposite to a refrigerant flow direction of the intermediate pressure refrigerant shut-off valve 60 and to reduce vibration occurrence of the intermediate pressure refrigerant guide pipe P5, it is desirable that the intermediate pressure refrigerant shut-off valve 60 be maintained to be opened.

In a case in which supercooling control is required in order to prevent occurrence of noise due to a low rotation frequency or low operating load of the dual inverter compressor 10, a long main pipe of 90 cm or more, or head installation between the indoor unit 2 and the outdoor unit 1, the electric expansion valve 30 is opened so that heat-exchange of the refrigerant is performed in the inner heat exchanger 20, and the opening and closing valve 50 is opened so that the intermediate pressure refrigerant is prevented from being injected to the dual inverter compressor 10, whereby the intermediate pressure refrigerant generated in the inner heat exchanger 20 is moved along the intermediate pressure refrigerant branch pipe B2 to be stored in the accumulator A, as shown in FIGS. 9 and 10.

When opening the electric expansion valve 30, among the refrigerants moved from the indoor heat exchanger 5 to the outdoor heat exchanger 4, the refrigerant bypassed through the bypass pipe B1 and the refrigerant moved from the indoor heat exchanger 5 to the outdoor heat exchanger 4 are heat-exchanged in the inner heat exchanger 20, so that the refrigerant bypassed through the bypass pipe B1 through the heat-exchange is superheated and moved along the intermediate pressure refrigerant branch pipe B2 branched in the intermediate pressure refrigerant guide pipe P5 to be stored in the accumulator A, and the refrigerant moved from the indoor heat exchanger 5 to the outdoor heat exchanger 4 is supercooled and moved to the outdoor heat exchanger 4.

In this instance, since the intermediate pressure refrigerant is prevented from being injected to the dual inverter compressor 10, the intermediate pressure refrigerant shut-off valve 60 should be shut off, but it is desirable that the intermediate pressure refrigerant shut-off valve 60 be maintained to be opened in order to reduce the chattering phenomenon that occurs when the refrigerant flows in a direction opposite to a refrigerant flow direction of the intermediate pressure refrigerant shut-off valve 60, and to reduce occurrence of vibration of the intermediate pressure refrigerant guide pipe P5 are reduced.

In FIG. 11, a cooling cycle at the time of a cooling operation of an air conditioner is shown, but there is a difference only in that the refrigerant flows in a direction opposite to the direction at the time of a heating operation shown in FIG. 5, and thus description of general refrigerant flow will be omitted.

As shown in FIGS. 11 and 12, in the same manner as the heating operation, when efficiency of the dual inverter compressor 10 is reduced during a cooling operation, an operating frequency of the dual inverter compressor 10 is increased or a discharge temperature of the dual inverter compressor 10 is increased. In order to improve the efficiency of the dual inverter compressor 10, the operating frequency of the dual inverter compressor 10 should be maintained at an optimal frequency or the discharge temperature should be reduced. Therefore, the intermediate pressure refrigerant is injected to the dual inverter compressor 10 in order to maintain the operating frequency of the dual inverter compressor 10 at the optimal frequency or reduce the discharge temperature.

In order to maintain the operating frequency of the dual inverter compressor 10 at the optimal frequency or reduce the discharge temperature, by performing heat-exchange between a refrigerant moved from the outdoor heat exchanger 4 to the indoor heat exchanger 5 in the inner heat exchanger 20 provided between the second refrigerant pipe P2 and the third refrigerant pipe P3 and a refrigerant that is bypassed to the bypass pipe B1 while being moved from the outdoor heat exchanger 4 to the indoor heat exchanger 5 and enters the inner heat exchanger 20, an intermediate pressure refrigerant is generated, and the generated intermediate pressure refrigerant is injected to the dual inverter compressor 10.

For this, first, in order for heat-exchange for generating the intermediate pressure refrigerant to be performed in the inner heat exchanger 20, a part of the refrigerant moved from the outdoor heat exchanger 4 to the indoor heat exchanger 5 is bypassed to the bypass pipe B1 by opening the electric expansion valve 30 provided in the bypass pipe B1.

The refrigerant bypassed to the inner heat exchanger 20 is heat-exchanged with the refrigerant moved from the outdoor heat exchanger 4 to the indoor heat exchanger 5 through the second refrigerant pipe P2 and the third refrigerant pipe P3 inside the inner heat exchanger 20, so that the refrigerant moved from the outdoor heat exchanger 4 to the indoor heat exchanger 5 through the heat-exchange is supercooled to be supplied to the indoor heat exchanger 5, and the refrigerant bypassed to the inner heat exchanger 20 is superheated to flow along the intermediate pressure refrigerant guide pipe P5.

A gas refrigerant injected to the inner heat exchanger 20 again is heat-exchanged with a liquid refrigerant inside the inner heat exchanger 20, so that the liquid refrigerant is supercooled through the heat-exchange to be supplied to the indoor heat exchanger 5 and the gas refrigerant is superheated to flow along the intermediate pressure refrigerant guide pipe P5.

In order for the intermediate pressure refrigerant flowing along the intermediate pressure refrigerant guide pipe P5 to be guided to the dual inverter compressor 10, the opening and closing valve 50 provided in the intermediate pressure refrigerant branch pipe B2 branched in the intermediate pressure refrigerant guide pipe P5 is shut off.

When shutting off the opening and closing valve 50, the intermediate pressure refrigerant cannot be moved to the intermediate pressure refrigerant branch pipe B2, and therefore the intermediate pressure refrigerant is moved along the intermediate pressure refrigerant guide pipe P5.

When the intermediate pressure refrigerant is moved along the intermediate pressure refrigerant guide pipe P5, the intermediate pressure refrigerant is injected to the dual inverter compressor 10 by opening the intermediate pressure refrigerant shut-off valve 60.

When an operating frequency of the dual inverter compressor 10 is maintained at an optimal frequency, or a discharge temperature of the dual inverter compressor 10 is reduced, the dual inverter compressor 10 should be protected by preventing the intermediate pressure refrigerant from being injected to the dual inverter compressor 10.

In a case in which supercooling control is not required while the intermediate pressure refrigerant is prevented from being injected to the dual inverter compressor 10 by maintaining the operating frequency of the dual inverter compressor 10 at the optimal frequency or reducing the discharge temperature, in order for the intermediate pressure refrigerant to be prevented from being injected to the dual inverter compressor 10, the electric expansion valve 30 is shut off so that heat-exchange of the refrigerant is not performed in the inner heat exchanger 20, as shown in FIGS. 13 and 14.

When the electric expansion valve 30 is shut off, the refrigerant is prevented from flowing to the bypass pipe B1 and the intermediate pressure refrigerant is not generated in the inner heat exchanger 20, and therefore the intermediate pressure refrigerant is prevented from being injected to the dual inverter compressor 10.

In this instance, since the intermediate pressure refrigerant is prevented from being injected to the dual inverter compressor 10, the opening and closing valve 50 should be shut off, but in order to prevent an increase in piping stress due to an internal flow of the intermediate pressure refrigerant guide pipe P5, it is desirable that the opening and closing valve 50 be maintained to be opened.

In addition, since the intermediate pressure refrigerant is prevented from being injected to the dual inverter compressor 10, the intermediate pressure refrigerant shut-off valve 60 should be also shut off, but in order to reduce a chattering phenomenon that occurs when a refrigerant flows in a direction opposite to a refrigerant flow direction of the intermediate pressure refrigerant shut-off valve 60 and to reduce vibration occurrence of the intermediate pressure refrigerant guide pipe P5, it is desirable that the intermediate pressure refrigerant shut-off valve 60 be maintained to be opened.

In a case in which supercooling control is required in order to prevent occurrence of noise due to a low rotation frequency or low operating load of the dual inverter compressor 10, a long main pipe of 90 cm or more, or head installation between the indoor unit 2 and the outdoor unit 1, the electric expansion valve 30 is opened so that heat-exchange of the refrigerant is performed in the inner heat exchanger 20, and the opening and closing valve 50 is opened so that the intermediate pressure refrigerant is prevented from being injected to the dual inverter compressor 10, whereby the intermediate pressure refrigerant generated in the inner heat exchanger 20 is moved along the intermediate pressure refrigerant branch pipe B2 to be stored in the accumulator A, as shown in FIGS. 13 and 14.

When opening the electric expansion valve 30, among the refrigerants moved from the outdoor heat exchanger 4 to the indoor heat exchanger 5, the refrigerant bypassed through the bypass pipe B1 and the refrigerant moved from the outdoor heat exchanger 4 to the indoor heat exchanger 5 are heat-exchanged in the inner heat exchanger 20, so that the refrigerant bypassed through the bypass pipe B1 through the heat-exchange is superheated and moved along the intermediate pressure refrigerant branch pipe B2 branched in the intermediate pressure refrigerant guide pipe P5 to be stored in the accumulator A, and the refrigerant moved from the outdoor heat exchanger 4 to the indoor heat exchanger 5 is supercooled and moved to the indoor heat exchanger 5.

In this instance, since the intermediate pressure refrigerant is prevented from being injected to the dual inverter compressor 10, the intermediate pressure refrigerant shut-off valve 60 should be shut off, but it is desirable that the intermediate pressure refrigerant shut-off valve 60 be maintained to be opened in order to reduce the chattering phenomenon that occurs when the refrigerant flows in a direction opposite to a refrigerant flow direction of the intermediate pressure refrigerant shut-off valve 60, and to reduce occurrence of vibration of the intermediate pressure refrigerant guide pipe P5 are reduced.

As described above, according to one or more embodiments, during the cooling operation, the cooling operation is performed with a high frequency, the frequency may be moved to a region with superior efficiency by injecting the intermediate pressure refrigerant to the inverter compressor, and the discharge temperature of the inverter compressor may be reduced without any separate device.

Although a few embodiments have been shown and described, it would be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the disclosure, the scope of which is defined in the claims and their equivalents. 

What is claimed is:
 1. An air conditioner comprising: a dual inverter compressor that includes a first inverter compressor and a second inverter compressor and compresses a refrigerant at a high temperature and at a high pressure; an indoor heat exchanger that liquefies the refrigerant supplied from the dual inverter compressor; an expansion valve that decompresses and expands the refrigerant supplied from the indoor heat exchanger; an outdoor heat exchanger that vaporizes the refrigerant supplied from the expansion valve; a bypass pipe that is bypassed in a refrigerant pipe for connecting the indoor heat exchanger and the outdoor heat exchanger, and in which an electric expansion valve is installed; an inner heat exchanger that is provided between the indoor heat exchanger and the outdoor heat exchanger, and is connected with the bypass pipe to generate an intermediate pressure refrigerant through heat exchange of the refrigerant moved from the indoor heat exchanger to the outdoor heat exchanger and the refrigerant bypassed to the bypass pipe; an intermediate pressure refrigerant guide pipe that guides the intermediate pressure refrigerant generated through the heat exchange in the inner heat exchanger to the dual inverter compressor, and in which an intermediate pressure refrigerant shut-off valve for controlling injection of the intermediate pressure refrigerant to the dual inverter compressor or controlling the injection to be prevented, and an intermediate pressure refrigerant spraying port for spraying the intermediate pressure refrigerant that has passed through the intermediate pressure refrigerant shut-off valve to the dual inverter compressor are installed; and an intermediate pressure refrigerant branch pipe that is branched in the intermediate pressure refrigerant guide pipe, and in which an opening and closing valve for controlling the intermediate pressure refrigerant to be injected to the dual inverter compressor along the intermediate pressure refrigerant guide pipe is installed.
 2. The air conditioner according to claim 1, wherein the inner heat exchanger performs heat exchange between the refrigerant that is moved from the indoor heat exchanger to the outdoor heat exchanger and the refrigerant that is bypassed to the bypass pipe and enters the inner heat exchanger, so that the refrigerant moved from the indoor heat exchanger to the outdoor heat exchanger is supercooled and the refrigerant bypassed to the bypass pipe and entering the inner heat exchanger is superheated.
 3. The air conditioner according to claim 1, further comprising: an accumulator that is provided so as to be connected with the intermediate pressure refrigerant branch pipe, and stores the intermediate pressure refrigerant injected through the intermediate pressure refrigerant branch pipe when the opening and closing valve is opened.
 4. The air conditioner according to claim 1, wherein the intermediate pressure refrigerant branch pipe is provided so as to be connected to a refrigerant pipe, which connects the intermediate pressure refrigerant branch pipe to the dual inverter compressor, and which enables the intermediate pressure refrigerant injected through the intermediate pressure refrigerant branch pipe to be supplied to the dual inverter compressor together with a refrigerant moved from the outdoor heat exchanger to the dual inverter compressor when the opening and closing valve is opened.
 5. The air conditioner according to claim 1, wherein the intermediate pressure refrigerant shut-off valve includes a first intermediate pressure refrigerant shut-off valve for controlling injection of the intermediate pressure refrigerant to the first inverter compressor and a second intermediate pressure refrigerant shut-off valve for controlling injection of the intermediate pressure refrigerant to the second inverter compressor.
 6. The air conditioner according to claim 5, wherein a muffler is provided between the first inverter compressor and the first intermediate pressure refrigerant shut-off valve and between the second inverter compressor and the second intermediate pressure refrigerant shut-off valve.
 7. The air conditioner according to claim 1, further comprising: a control unit that controls the electric expansion valve, the opening and closing valve, and the intermediate pressure refrigerant shut-off valve.
 8. An air conditioner comprising: a dual inverter compressor that includes a first inverter compressor and a second inverter compressor, and compresses a refrigerant at a high temperature and at a high pressure; an outdoor heat exchanger that liquefies the refrigerant supplied from the dual inverter compressor; an expansion valve that decompresses and expands the refrigerant supplied from the outdoor heat exchanger; an indoor heat exchanger that vaporizes the refrigerant supplied from the expansion valve; a bypass pipe that is bypassed in a refrigerant pipe for connecting the outdoor heat exchanger and the indoor heat exchanger, and in which an electric expansion valve is installed; an inner heat exchanger that is provided between the outdoor heat exchanger and the indoor heat exchanger and is connected with the bypass pipe to generate an intermediate pressure refrigerant through heat exchange of the refrigerant moved from the outdoor heat exchanger to the indoor heat exchanger and the refrigerant bypassed to the bypass pipe; an intermediate pressure refrigerant guide pipe that guides the intermediate pressure refrigerant generated through the heat exchange in the inner heat exchanger to the dual inverter compressor, and in which an intermediate pressure refrigerant shut-off valve for controlling injection of the intermediate pressure refrigerant to the dual inverter compressor or controlling the injection to be prevented and an intermediate pressure refrigerant spraying port for spraying the intermediate pressure refrigerant that passed through the intermediate pressure refrigerant shut-off valve to the dual inverter compressor are installed; and an intermediate pressure refrigerant branch pipe that connects the intermediate pressure refrigerant guide pipe and an accumulator, and in which an opening and closing valve for controlling the intermediate pressure refrigerant to be injected to the dual inverter compressor along the intermediate pressure refrigerant guide pipe or to be discharged to the accumulator is installed.
 9. The air conditioner according to claim 8, wherein the inner heat exchanger performs heat exchange between the refrigerant that is moved from the outdoor heat exchanger to the indoor heat exchanger and the refrigerant that is bypassed to the bypass pipe and enters the inner heat exchanger, so that the refrigerant moved from the outdoor heat exchanger to the indoor heat exchanger is supercooled and the refrigerant bypassed to the bypass pipe and entering the inner heat exchanger is superheated.
 10. The air conditioner according to claim 8, wherein the accumulator stores the intermediate pressure refrigerant injected through the intermediate pressure refrigerant branch pipe when the opening and closing valve is opened.
 11. The air conditioner according to claim 8, wherein the intermediate pressure refrigerant branch pipe is provided so as to be connected to a refrigerant pipe, which connects the intermediate pressure refrigerant branch pipe to the dual inverter compressor, and which enables the intermediate pressure refrigerant injected through the intermediate pressure refrigerant branch pipe to be supplied to the dual inverter compressor together with a refrigerant moved from the indoor heat exchanger to the dual inverter compressor when the opening and closing valve is opened.
 12. The air conditioner according to claim 8, wherein the intermediate pressure refrigerant shut-off valve includes a first intermediate pressure refrigerant shut-off valve for controlling injection of the intermediate pressure refrigerant to the first inverter compressor and a second intermediate pressure refrigerant shut-off valve for controlling injection of the intermediate pressure refrigerant to the second inverter compressor.
 13. The air conditioner according to claim 12, wherein a muffler is provided between the first inverter compressor and the first intermediate pressure refrigerant shut-off valve and between the second inverter compressor and the second intermediate pressure refrigerant shut-off valve.
 14. The air conditioner according to claim 8, further comprising: a control unit that controls the electric expansion valve, the opening and closing valve, and the intermediate pressure refrigerant shut-off valve.
 15. A method for controlling a heating operation of an air conditioner including a dual inverter compressor having a first inverter compressor and a second inverter compressor, an indoor heat exchanger, and an outdoor heat exchanger, the method comprising: enabling a partial refrigerant to be expanded in a bypass pipe that is bypassed from a refrigerant pipe for connecting the indoor heat exchanger and the outdoor heat exchanger by opening an electric expansion valve installed in the bypass pipe; generating an intermediate pressure refrigerant by supplying the refrigerant of the bypass pipe to the inner heat exchanger installed in the refrigerant pipe for connecting the indoor heat exchanger and the outdoor heat exchanger; shutting off an opening and closing valve that is provided in an intermediate pressure refrigerant branch pipe branched in an intermediate pressure refrigerant guide pipe for connecting the inner heat exchanger and the dual inverter compressor so that the intermediate pressure refrigerant is moved through the intermediate pressure refrigerant guide pipe; and enabling the intermediate pressure refrigerant to be injected to the dual inverter compressor through the intermediate pressure refrigerant guide pipe by opening the intermediate pressure refrigerant shut-off valve provided in the intermediate pressure refrigerant guide pipe.
 16. The method according to claim 15, wherein, when the electric expansion valve is opened, the refrigerant bypassed to the bypass pipe is expanded in the electric expansion valve and then injected to the inner heat exchanger to be heat-exchanged with the refrigerant moved from the indoor heat exchanger to the outdoor heat exchanger, the refrigerant moved from the indoor heat exchanger to the outdoor heat exchanger is supercooled through heat exchange to be supplied to the outdoor heat exchanger, and the refrigerant bypassed to the bypass pipe is supplied to the dual inverter compressor in a state of absorbing heat.
 17. A method for controlling a heating operation of an air conditioner including a dual inverter compressor having a first inverter compressor and a second inverter compressor, an indoor heat exchanger, and an outdoor heat exchanger, the method comprising: preventing a refrigerant from flowing to a bypass pipe that is bypassed in a refrigerant pipe for connecting the indoor heat exchanger and the outdoor heat exchanger and is connected with an inner heat exchanger provided in the refrigerant pipe, by shutting off an electric expansion valve installed in the bypass pipe, so that an intermediate pressure refrigerant is prevented from being injected to the dual inverter compressor.
 18. The method according to claim 17, wherein, when the intermediate pressure refrigerant is prevented from being injected to the dual inverter compressor by shutting off the electric expansion valve, an opening and closing valve that is installed in an intermediate pressure refrigerant branch pipe branched in an intermediate pressure refrigerant guide pipe for connecting the inner heat exchanger and the dual inverter compressor is maintained to be opened, so that an increase in piping stress due to an internal flow of the intermediate pressure refrigerant guide pipe is prevented.
 19. The method according to claim 18, wherein, when the intermediate pressure refrigerant is prevented from being injected to the dual inverter compressor by shutting off the electric expansion valve and opening the opening and closing valve, the intermediate pressure refrigerant shut-off valve provided in the intermediate pressure refrigerant guide pipe is maintained to be opened, so that chattering that occurs when the refrigerant flows in a direction opposite to a refrigerant flow direction of the intermediate pressure refrigerant shut-off valve, and occurrence of vibration of the intermediate pressure refrigerant guide pipe are reduced.
 20. A method for controlling a heating operation of an air conditioner including a dual inverter compressor having a first inverter compressor and a second inverter compressor, an indoor heat exchanger, and an outdoor heat exchanger, the method that prevents injection of an intermediate pressure refrigerant to the dual inverter compressor, and controls a refrigerant moved from the indoor heat exchanger to the outdoor heat exchanger to be supercooled, the method comprising: enabling a refrigerant to be bypassed to a bypass pipe by opening an electric expansion valve installed in the bypass pipe that is bypassed in a refrigerant pipe for connecting the indoor heat exchanger and the outdoor heat exchanger and connected to an inner heat exchanger provided in the refrigerant pipe; and preventing the intermediate pressure refrigerant from being injected to the dual inverter compressor by opening an opening and closing valve installed in an intermediate pressure refrigerant branch pipe branched in an intermediate pressure refrigerant guide pipe for connecting the inner heat exchanger and the dual inverter compressor so that the intermediate pressure refrigerant generated in the inner heat exchanger is moved through the intermediate pressure refrigerant branch pipe to be stored in an accumulator connected with the intermediate pressure refrigerant branch pipe.
 21. The method according to claim 20, wherein, when the intermediate pressure refrigerant is prevented from being injected to the dual inverter compressor by opening the electric expansion valve and the opening and closing valve, an intermediate pressure refrigerant shut-off valve provided in the intermediate pressure refrigerant guide pipe is maintained to be opened, so that chattering that occurs when the refrigerant flows in a direction opposite to a refrigerant flow direction of the intermediate pressure refrigerant shut-off valve, and occurrence of vibration of the intermediate pressure refrigerant guide pipe are reduced.
 22. A method for controlling a cooling operation of an air conditioner including a dual inverter compressor having a first inverter compressor and a second inverter compressor, an indoor heat exchanger, and an outdoor heat exchanger, the method comprising: enabling a partial refrigerant to be expanded in a bypass pipe that is bypassed from a refrigerant pipe for connecting the outdoor heat exchanger and the indoor heat exchanger by opening an electric expansion valve installed in the bypass pipe; generating an intermediate pressure refrigerant by supplying the refrigerant of the bypass pipe to the inner heat exchanger installed in the refrigerant pipe for connecting the outdoor heat exchanger and the indoor heat exchanger; shutting off an opening and closing valve that is provided in an intermediate pressure refrigerant branch pipe branched in an intermediate pressure refrigerant guide pipe for connecting the inner heat exchanger and the dual inverter compressor so that the intermediate pressure refrigerant is moved through the intermediate pressure refrigerant guide pipe; and enabling the intermediate pressure refrigerant to be injected to the dual inverter compressor through the intermediate pressure refrigerant guide pipe by opening the intermediate pressure refrigerant shut-off valve provided in the intermediate pressure refrigerant guide pipe.
 23. The method according to claim 22, wherein, when the electric expansion valve is opened, the refrigerant bypassed to the bypass pipe is expanded in the electric expansion valve and then injected to the inner heat exchanger to be heat-exchanged with the refrigerant moved from the outdoor heat exchanger to the indoor heat exchanger, the refrigerant moved from the outdoor heat exchanger to the indoor heat exchanger is supercooled through heat exchange to be supplied to the indoor heat exchanger, and the refrigerant bypassed to the bypass pipe is supplied to the dual inverter compressor in a state of absorbing heat.
 24. A method for controlling a cooling operating of an air conditioner including a dual inverter compressor having a first inverter compressor and a second inverter compressor, an indoor heat exchanger, and an outdoor indoor exchanger, the method comprising: preventing a refrigerant from flowing to a bypass pipe that is bypassed in a refrigerant pipe for connecting the outdoor heat exchanger and the indoor heat exchanger and is connected with an inner heat exchanger provided in the refrigerant pipe, by shutting off an electric expansion valve installed in the bypass pipe, so that an intermediate pressure refrigerant is prevented from being injected to the dual inverter compressor.
 25. The method according to claim 24, wherein, when the intermediate pressure refrigerant is prevented from being injected to the dual inverter compressor by shutting off the electric expansion valve, an opening and closing valve that is installed in an intermediate pressure refrigerant branch pipe branched in an intermediate pressure refrigerant guide pipe for connecting the inner heat exchanger and the dual inverter compressor is maintained to be opened, so that an increase in piping stress due to an internal flow of the intermediate pressure refrigerant guide pipe is prevented.
 26. The method according to claim 25, wherein, when the intermediate pressure refrigerant is prevented from being injected to the dual inverter compressor by shutting off the electric expansion valve and opening the opening and closing valve, the intermediate pressure refrigerant shut-off valve provided in the intermediate pressure refrigerant guide pipe is maintained to be opened, so that chattering that occurs when the refrigerant flows in a direction opposite to a refrigerant flow direction of the intermediate pressure refrigerant shut-off valve, and occurrence of vibration of the intermediate pressure refrigerant guide pipe are reduced.
 27. A method for controlling a cooling operation of an air conditioner including a dual inverter compressor having a first inverter compressor and a second inverter compressor, an indoor heat exchanger, and an outdoor heat exchanger, the method that prevents injection of an intermediate pressure refrigerant to the dual inverter compressor, and controls a refrigerant moved from the indoor heat exchanger to the outdoor heat exchanger to be supercooled, the method comprising: enabling a refrigerant to be bypassed to a bypass pipe by opening an electric expansion valve installed in the bypass pipe that is bypassed in a refrigerant pipe for connecting the outdoor heat exchanger and the indoor heat exchanger and connected to an inner heat exchanger provided in the refrigerant pipe; and preventing the intermediate pressure refrigerant from being injected to the dual inverter compressor by opening an opening and closing valve installed in an intermediate pressure refrigerant branch pipe branched in an intermediate pressure refrigerant guide pipe for connecting the inner heat exchanger and the dual inverter compressor so that the intermediate pressure refrigerant generated in the inner heat exchanger is moved through the intermediate pressure refrigerant branch pipe to be stored in an accumulator connected with the intermediate pressure refrigerant branch pipe.
 28. The method according to claim 27, wherein, when the intermediate pressure refrigerant is prevented from being injected to the dual inverter compressor by opening the electric expansion valve and the opening and closing valve, an intermediate pressure refrigerant shut-off valve provided in the intermediate pressure refrigerant guide pipe is maintained to be opened, so that chattering that occurs when the refrigerant flows in a direction opposite to a refrigerant flow direction of the intermediate pressure refrigerant shut-off valve, and occurrence of vibration of the intermediate pressure refrigerant guide pipe are reduced. 